1. Field of the Invention
The present invention relates to an improved method and apparatus for simultaneously exchanging various automotive fluids. More specifically, the present invention discloses a method and apparatus for exchanging the power steering fluid of a vehicle using a particular device. The device includes a control module which enables the user to control the flow rate of new fluid into the power steering reservoir relative to the flow rate of old fluid being removed. The module further enables the user to set a lever at a particular setting once the flow rates are controlled such that the fluid level within the reservoir will remain constant.
2. Description of the Related Art
The typical automobile has numerous fluid systems. These fluids, in order for the vehicle to be properly maintained, must be changed out periodically. This means simply removing the old (or “dirty”) fluid and replacing it with clean new fluid. This is true with respect to motor oil, transmission fluid, differential fluid, and power steering fluid.
With respect to power steering fluid, special problems are encountered. The power steering fluid is used as part of the steering hydraulic system of the vehicle. The hydraulic system consists of a pump, hoses and lines to transport the fluid, cylinders and pistons to create motion, and gear drives or turbines to turn shafts. Numerous valves are also used to control the flow and activate the systems. These valves are often small and very sensitive to debris or any form of solid contaminants. The amount of power steering fluid present in the system in an automobile is actually very small. It usually amounts to one quart or less. This small amount of fluid has traditionally been difficult to replace. This is because there is no easy way to drain and refill the system. In fact, most vehicles systems have no built-in way to be drained or refilled.
One reason access to the power steering system is made limited, is that upon draining and refilling of the fluid, air is often trapped within the system. Trapped air in a system can damage components and diminish system performance. Many methods have been used in the prior art to change out steering fluid. One such method involves simply removing the pump return line from the vehicle's system. This allows the pump to dispense the old fluid into a separate container which is placed beneath the vehicle. The new fluid is either sucked into or poured into the reservoir. This method is possible on only a few power steering system designs where the lines are accessible and removable. However, even in the rare instances that using this method is possible, there is an ever-present danger that air will get trapped within the system. Additionally, disconnecting these lines and then reconnecting them can result in leaks. Because of the small amount of fluid in the system to begin with, even small leaks can cause the system pump to cavitate and thus be destroyed.
A second method that is known in the prior art that, unlike the first method, does not disturb the plumbing of the power steering system (does not involve the removal of lines), is shown in FIG. 9. Referring to FIG. 9, the prior art device 210 has both fresh fluid and used fluid conduits referenced at 256 and 262 respectively. The system also uses first and second pumps, 216 and 218, through which conduits 256 and 262 extend. Pumps 216 and 218 are not variable, and are switched on and off using switches. Conduit 262 is used to withdraw old fluid from reservoir 258 and dump it into a container 274. New fluid conduit 256 draws new fluid out of container 248 and then distributes it into the reservoir 258. Upon closer inspection, it can be seen that conduit 256 distributes fluid into the reservoir 258 at a level above that which dirty fluid is withdrawn from the reservoir in conduit 262.
The details regarding this prior art system may be seen in U.S. Pat. No. 5,415,247 issued to Knorr (“Knorr”). Though a significant achievement over earlier power steering fluid exchange systems, Knorr still presented problems when used in the field. One of these problems involved its inability to cope with the differences in circulation rates of different power steering fluid systems. Because the Knorr pumping system does not allow the user to adjust the flow rates of each individual conduit, the user was required to maintain a particular fluid level in the reservoir by manipulating the on and off switches of pumps 216 and 218. This made the procedure labor intensive. This is because the user would have to keep an eye on the level in the reservoir, which contained very little fluid to begin with, to make sure that (i) the fluid would not overflow, and (ii) the reservoir would not run dry. Overflow of the reservoir would create a mess, whereas were the reservoir to run dry, air would be introduced into the system and possibly cause damage thereto.
Sometimes, two technicians would be needed. This is because one user alone could not monitor the level of fluid in the reservoir at the same time as having access to the pump on/off switches. The relative remoteness of pump controls for pumps 216 and 218 from the reservoir would create this problem. Thus, constant attention by the user or users was required. Therefore, there was a need for a way to control the flow rates in conduits 256 and 262 so that they would remain at a rate relative to one another that would cause the level in the reservoir 258 to remain at a constant and not to overflow or run dry. Further, there was a need in the art for a control module that would enable the user to be able to monitor the level of fluid in the reservoir simultaneously with being able to adjust the relative flow rates of the conduits but also to be able to turn the pumps off and on with one controller.